Steam boiler combustion control unit



July 2, 1963 A. A. KRAFT 3,096,020

STEAM BOILER COMBUSTION CONTROL UNIT Fiied June 4, 1959 5 sheets-sheet 1 l l /5 2a /a n July 2, 1963 A. A. KRAFT STEAM BOILER COMBUSTION CONTROL UNIT 5 Sheets-Sheet 2 Filed June 4, 1959 iuvsnfon men/wz A, loe/9F7- /g u. H/s ATTORNEY July 2, 1963 A. A. KRAFT 3,096,020

STEAM BOILER COMBUSTION CONTROL UNIT n Filed June 4, 1959 5 Sheets-Sheen'. 3

INVENTQR Y mer/1u@ a; Knfr /2/ fini @/2@ F/g 40 July 2, 1963 A. A. KRAFT 3,096,020

STEAM BoILER COMBUSTION CONTROL UNIT Filed June 4, 1959 5 sheets-sheet 4 i@ Q (ID 7o /s7 /sa 52 INVENTOR. F/g. 5

July 2, 1963 A. A. KRAFT 3,096,020

STEAM BOILER COMBUSTION CONTROL UNIT Filed June 4, 1959 5 Sheets-Sheet 5 INVENTOR. Ami-wle A. KRAFT H/S ATTORA/e-Y United States Patent O 3,6%,629 STEAM BGILER CGMEUS'HGN CGNTRGL UNlT Arthur A. Kraft, Parma, Ghio, assigner to Cleveland Controls, Inc. Filed .lune 4, i959, Ser. No. $518,664 6 Claims. (Cl. 23o-14) This invention relates to a combustion control unit for controlling the ilow of fuel, or air, or both, to a burner.

Many large capacity heating systems which use a fluid fuel, such as oil or gas, operate on the principle of controlling the rate of fuel flow to the burner in response to the rate of air flow to the burner, or vice versa. The rate of air flow is under the control of a master regulator, which operates in response to `the demand on the heating system. For example, if the demand is for more heat, the master regulator will increase the `air flow, and the fuel ow will lbe increased in response to the increasing `air ow.

In order to have proper combustion, it is necessary to have the proper proportions of fuel and air in the combustible fuel-air mixture at the burner. lVhile it is true that, for any burner, ian increase in the air ow requires an increase in the fuel flow to obtain proper cornbustion, the relationship of these flows for optimum combustion varies with fuels and from one installation to the next. Therefore, to obtain optimum combustion in any given installation requires that the optimum fuel-air ratios be determined empirically f-or that particular installation. Commonly, this is done by adjusting the fuel-air ratio to produce optimum CO2 in the stack lover =the entire range of combustion rates established by `themaster regulator.

In the past it has been necessary to use extremely precise and complicated cam-operated valves of special design to control one of the ilow rates of either fuel `or air.

The present invention is directed to a novel control unit which -obviates the need for such a special, expensive valve. The present control unit incorporates within itself an adjustable cam device which may be adj-usted to provide the optimum fuel-air ratio at the burner regardless of the individual characteristics of the valve which is operated by the control unit.

Accordingly, it is an object of this invention to provide a novel combustion control unit for a burner.

Another object of this invention is to provide such a control unit which avoids the need for a cam-operated valve and thereby reduces the cost of the installation, at the same time providing an extremely precise control.

Another object of the invention is to provide a device which enables a greater control over the sensitivity of the system, the range through which the system operates and enabling the ratio of fuel to air to be quickly and easily changed.

Other objects and advantages of this invention will be apparent from the following description of a presently preferred embodiment thereof, which is illustrated in the accompanying drawings.

In the drawings:

FIGURE 1 is a schematic view of a` steam boiler system which incorporates the present control unit;

FlGU-RE 2 is an elevational view of a complete control and regulator unit with the cover removed;

FIGURE 3 is a fragmentary section taken from the line 3 3 of FIG. 2;

FIGURE 4 is an elevationalview "of the regulator unit removed from the housing, taken from the rear side as viewed in FIGURE v2;

FIG. 4a is a fragmentary View, partly in section and partly in elevation, of the diaphragm connecting linkage;

FIGURE 5 is a plan View thereof;

FiGURES 6 and 7 are elevational views from opposite ends;

Y 3,096,020 Patented July 2, 1963 ICC FIGURE 8 is a plan view of the regulator unit base with the parts removed;

y FIGURE 9 is a fragmentary section taken on the line 9 9 of FIG. 5;

FIGURE l0 is a fragmentary section taken on the line lil-llt) of FIG. 2; and

FIGURE l1 is an electrical diagram of lthe complete control unit.

When the steam pressure in a boiler increases or decreases, a master regulator, which is responsive to the steam pressure, is operated. If the pressure goes down, the control arm on the master regulator moves in a direction to control apparatus which supplies more air to a burner. The master regulator therefore controls the amount of air supplied and the air supply is increased as the steam pressure decreases and decreases upon an increase in steam pressure.

The amount of lfuel to be supplied to the burner is determined by the `amount of air `being supplied.

The present system includes a unit which measures the amount of air flow through the burner and controls the supply of the desired amount 4of fuel accordingly. The amount of `air being supplied can be determined by the pressure drop, across the burner, across the boiler, or, across the damper in the air duct or stack. As a matter of fact it can be sensed at any place where the air flow can be measured.

The ldifferential in Iair pressure between two points is applied to a diaphragm in the sensing unit. The position of the diaphragm is therefore determined by the differential in pressure. The diaphragm is coupled to a member which actuates a pair of switches. The switches control the switching of current in a circuit to actuate a motor which operates a control arm that is connected to afuel valve which regulates the flow of fuel in the burner. The control arm and switch operating member are connected to a balance member whereby the two act in opposition when a certain point has been reached to maintain the flow lof products for combustion in the proper ratio and volume. The balance member is adjustable so that the ratio of fuel and air may be adjusted.

lReferring first to FIG. l, which is a general schematic View of the system, a boiler 10 is illustrated, being provided with a stack 11 rand a suitable burner 12 which extends into the combustion chamber. An air supply 14 under control of a master regulator 15, which is in turn controlled by steam pressure from a line 16 connected to the boiler, is connected to the burner. The master regulator controls the delivery of air to the burner at a rate which depends upon the demand on the `heating system. As previously stated, the product for combustion' which -is thus supplied may be either fuel or air. The present system will be described however in connection with the supply of air being determined by steam pressure.

The amount of air flowing to the burner is sensed by a sensing unit 5. Lines 17 and 18 which are connected to the stack 11 and to the combustion chamber of the boiler respectively an'd which lines also connect to chambers 20a and Ztl'b, FIG. 4, in a housing Ztl of the unit, the chambers being separated by `a flexible diaphragm 19. The flexible diaphragm 19 is clamped between the flanges of the housing' 20 and, at its mid portion, a rod 22 is connected to the diaphragm by washers 23 and nuts 24 which are threaded on the rod and clamp the diaphragm therebetween.

The diaphragm controls the operation of the fuel control unit, `which is coupled to a fuel control Valve Z1 in the fuel supply line to the burner. The operation is such that the fuel flow lis increased if the air ilow is increased, and the fuel ilow is decreased if Ithe air ow is decreased.

An electric motor 25,- in the fuel control unit, FIG. 2,

rotates a drive screw 26 which is threaded in a follower or nut 27, that is connected to a hollow shaft or control arm 28. Depending -upon which direction the motor is turning the -screw 26, the follower 27 and control arm 23 are moved axially toward or away from the motor or from right to left as viewed in FIGS. 2 and f3 of the drawings to control the setting of fuel valve 21 accordingly. The arm 28 has an eye on the end which is connected to the fuel valve 21 by a suitable linkage such as `a link 29.

The control arm 23, FIG. 3, is connected to a plate 30 by a pin 31 and bracket 32, the plate having a pair of ears 33 whereby it is slidably journalled on a pair of rods 34 secured to the end wall 35 of the casing at one end .and a bracket 36 secured to the back wall of the casing at the other end. The plate Sil' may thus be reciprocated as the arm 28 moves in and out. As best shown in FIG. 2, the plate 30 is formed with an inverted V-shaped slot comprised of legs 40 and 41 which extend at right angles to each other. Above the apex of the slot an outwardly extending pin 42 is provided.

The sensing yunit senses a differential of pressure and moves a switch operating member which operates switches to turn on the motor 2S. The motor 25 actuates the control arm 28 which in turn, after reaching a certain position operates the switch operating member in the opposite `direction to open the switches 'which deenergize the motor, leaving the arm and the valve connected thereto in a certain predetermined position.

The housing 2t) supports :a base plate 50, the base plate being spaced from and above the housing by spacers 51 and held thereon by screws which extend through the base plate and spacers and are threaded into bosses on the housing. At the front of the base plate there is provided a -downwardly extending panel 52. The entire sensing unit is readily removable from the main casing being held therein by screws that extend through the bottom of the casing and Iare threaded into bosses on the housing Near one end of the base plate 50, FIG. 5, a bearing bracket 55 is provided having a pair of upstanding flanges 56 and 57. These flanges provide :a support for a shaft 58 which is rotatably journalled in bearings in' the bracket. One end of the shaft is held against sliding by :a collar 59 and the other end beyond the flange 57 carries a spur gear 60 which is secured to the shaft. The shaft, adjacent the spur gear 60, carries a cam lever 62. This lever may be secured to the shaft or the gear so that when the lever is moved it rotates the gear. Near the upper end, the lever 62 carries 1a pin 63 which extends into the V cam slot 40-41 in the plate 30. At its upper end, the lever is provided with a fork comprised of the two spaced arms 64 the upper extremities of which are curved outwardly, the arms being disposed on' opposite sides of the pin 42 carried by the plate 30. The plate is thus connected to the lever 62 and lthe connection is such that rectilinear motion of the cam plate is converted into substantially proportional rotary motion of the -gear 60.

As illustrated in PIG. 2, where the arm 28 is substantially the mid-portion of its travel and the lever arm 62 is extending vertically, the pin 63` is at the apex of the V slot and the pin 42 is down in the slot formed by the fork arms 64. If the control arm should move to the right, the pin 42 would contact with the right hand side fork 64 and immediately start the lever arm 62 and its gear moving clockwise. As the arm 28 rnoves out and the lever 62 is swung farther, the pin 63 moves into the slot which now takes over the control of the lever 62. Continued movement of the arm 2S causes the lever 62 to be swung further clockwise because of the slant of the cam slot 40". The curved formation of the arms 64 permit this movement relative to the pin 42. It will be appreciated that should the arm 28 move in the other direction, the opposite or counter-clockwise movement of the lever 62 is effected. It is yapparent that the cam slots 4il-41 could be slightly curved so that the linear movement of the arm 28 is converted into an exactly proportionate amount of rotatory movement of the gear 60 but that in' the interest of economy in manufacture, straight cam slots are provided -to provide a substantially proportionate conversion of linear to rotary motion.

The gear 6d is in mesh with a smaller gear 70 that is secured on a shaft 71. The shaft is rotatably journalled in the flange 57 of the bearing bracket 55 and in the flange 72 of a bracket 73 secured to the top of the base. The shaft 71 is held against longitudinal movement in the flange 57 by the gear 70 which is on one side of the flange and a collar 74 secured to the shaft on the other side of the ilange. On the end of the shaft 71 which extends over the mid-line of the base there is secured a lever 76 which has a spring 77 secured to its end the other end of the spring being secured at its end to the edge of the base at 78. This causes the gears to always be pressure loaded, eliminating back lash.

The other end of the shaft extends beyond the flange 72 of the support bracket and at the end carries an adjustable cam body. A spacer sleeve 71' is disposed around the shaft between the cam and the bracket to enable the cam to be quickly adjusted in its proper longitudinal position on the shaft. The cam includes a hub 80, whereby it is secured to the shaft 71 and an outwardly extending semi-circular body 31. A plurality of adjusting screws S2 extend through the body in spaced relation to each other and slightly spaced from the periphery of the semi-circular portion of the body and parallel to the axis of the hub. Thes screws are disposed in threaded apertures in the body and ar sufficiently long that they can be extended well beyond the side of the body as can best be seen in FIG. 7. Once the position of the screws is determined they are locked into position by set screws 83 which are threaded into radially extending threaded openings in the periphery of the body, the openings communicating with the openings for the screws 82.

The cam surface proper is determind by the setting of the adjusting screws and comprises a flexible metallic plate 84, having an edge contour approximately the same as the cam body, secured to the cam body by a screw 85. This plate should preferably be made of a resilient material so that it will not take a permanent set. The position of the plate relative to the cam body is determined by the adjusting screws. As best shown in FIGS. 4 to 7, the rise of the plate is determined by the distance the screws are adjusted through the body. The cam plate should be heavy enough so that no decided bumps are present because of the contact of the screws and still resilient enough so that the cam contour can be determined in increments by the position of the screws. The ultimate result is a one-sided barrel cam the contour of which may be determined in very small increments and which is adjustable to the flow characteristics of the particular fuel valve being used.

When the lever `62 is moved in one direction the cam is moved in the other direction and because of the ratio of the gears 60-7tl, 45 movement of the cam is then proportionate to the movement of the control arm 28 and is in a direction to eventually counteract the movement of the diaphragm 19. The means whereby these forces are utilized to counteract and eventually balance each other includes a rocker beam, one end of which is actuated by the cam through a suitable linkage and the other end of which is actuated by the diaphragm 19 through another suitable linkage. The beam is supported at its center and the connections to the beam from the diaphragm and cam are on opposite ends of the beam. The support is also movable so that the points where the two linkages are connected to the beam may be simultaneously shifted to Vary the balance.

The beam support 90, FIG. 9, includes a slidable bracket having a pair of arm 90a at its upper end and between which the beam 92 is supported on a pivot pin 93. The lower end of the beam support is provided with a pair of slots 90b which engage with the base 50, the base being provided with an opening Stia-50h, FIG. 8, the wider part 50i; of the opening providing a clearance place where the support may be inserted into the opening and then moved into the narrow part of the opening to engage the marginal edges of the slot 5tba-50a which act as ways for the support. The bottom of the support 99 has a follower member 94 secured thereto and into which is threaded an adjusting screw 95, FIG. 10. The adjusting screw is secured to a bracket 96 on the underside of the base 50, being held against longitudinal movement by collars 97 and having a bevel gear 98 on its end in mesh with a bevel gear 99 on a shaft 100 which extends through the front panel 52 of the base and carries an operating knob 101 on its end.

When the knob 101 is rotated, the shaft 95 is rotated and the support 90 is slid along the ways 50a of the base to shift the support and along with it the beam 92.

The connection from the cam to the one end of the rocker beam is through a bell-crank lever. As shown in FIG. 6, the flange 72, on shaft support bracket 73, is provided with a pair of ears which provide a support for a pivot pin 1115. The bell-crank lever includes a pair of spaced arms 1116 which are pivotally journalled on the pivot pin 1&5 and extend upwardly on the opposite sides of the shaft 71 being joined together at the upper ends by a bridge portion 107, FIG. 4. The bridge portion extends forwardly toward the cam plate 84 and supports a cam engaging roller 108 mounted on a vertical pivot carried by the bridge 1117. Thus when the cam is moved the lever 106 is moved about its pivot 105.

At the lower end of the arms 1196, FIG. 5, one of the arms is provided with an oiset arm 110 which bears a roller 111 which is supported over and in contact with the beam 92. When the lever 106 is rocked, the arm 110 puts pressure onto or releases pressure from the beam 92 which is accordingly rocked.

As previously stated, the pressure sensitive diaphragm of the sensing unit is connected to a rod 22. The rod 22 extends upward through the upper chamber of the housing where it passes through a ilexible seal 120. The rod extends through the seal and through a plate 121 which lies in an opening 122 in the base 5t), FIGS. The plate 121 is secured to the base 5t) by a spring hinge connection 123 at one end. This leaves the end which the rod goes through free to move except for its connection to the rod, The rod 22 has a fulcrum nut 125 threaded thereon, the nut having knife edges which seat against the underside of the plate 121. Above the plate a helical spring 126, FIG. 6, surrounds the rod, the lower end bearing against the top of the plate 121 and the upper end bearing against a head 127 on the end of the rod. The head 127 is provided with a slot 128 and a link 129 is pivotally secured in the slot and extends upwardly from the head 127.

An inverted U-shaped bracket, FIG. 7, is secured to the end of the base and comprises legs 132 which are secured to the base at opposite sides of and straddling the pressure plate 121. The upper endl of the bracket is provided with a bridge 133 connecting the two legs. As can be seen from FGS. 4 and 5, the bridge is narrower than the legs and is provided with a downturn flange 134. A bar 13S is supported from the bridge by spring hinges at each end. Each of the hinges includes a at spring 136 which is secured to the top of the bridge by a screw and which extends under the bar and is attached thereto by a screw. Another ilat spring 137 is secured to the inner face of the bar by a screw and attached to the ilange 134 by another screw. Thus, the bar is supported by a substantially frictionless hinge which requires no lubrication and which enables the bar to be easily moved from its CTL normal position but which movement is resisted as the bar is turned from its normal position. It however lalways returns to its normal position when released due to the spring hinge. This is the same type of hinge construction as used to support the pressure plate 121.

A U-shaped lever, FIG. 5, is secured to the top of the bar by screws 14d and includes a base 141 and legs 142 and 143. The leg 143 extends over the rocker beam 92 and has secured to its underside a spring member 145, FIGS. 2 and 3, having a yoke 146` on its end which carries a roller 147 that rests on top of the beam 92. The position of the roller relative to the leg 143 may be adjusted vertically by a set screw 143 threaded through the arm and engaging the spring member 145 opposite the yoke. Movement of the set screw is resisted by a spring 149.

The lever 142-143 is held with the roller 147 spring pressed against the beam 92, under loaded conditions, by a tension spring 150, one end of which is secured to the arm 1413 and the other to the base.

The other arm 142 of the lever 142-143 is connected to the link 129 which connects to the pressure sensitive diaphragm. The same screws 1411 which hold the lever 14d- 143 to the bar 135 also clamp to the underside of the bar a flat spring member 155, FIG. 4, which extends beyond the end of the leg 142 and over the head 127 on the diaphragm rod 22, FIG. 5. FIhe end vof the spring 155 is provided with a pair of spaced arms 156 which carry a pivot pin 157 to which is attached a clamp link 158. The clamp link 158 is provided with an end which surrounds the link 129 and which may be clamped to that link at any desired position by a screw 160'.

A certain lfreedom. of movement of the spring member is realized with respect to the arm 1412 which overlies it due to the fact that the arm 142 is a heavy stift arm and the spring is a thin resilient member. The amount of resilient movement ofthe spring relative to the arm is contr-olled by the efrective length of the spring and the effective length of the spring is controlled by an adjustable clamp member 163;` which surrounds the arm 142 and spring 155. A set screw 164 is provided extending through the top of the clamp member for engagement with the arm 142 and when tightened pulls the spring tightly against the arm. The longitudinal position of the clamp on the arm and spring may be adjusted accurately by a screw 166 rotatably journalled in the bar 135 and having an end threaded into a projection 163 on the bottom of the clamp.

It will thus -be seen that there is provided means operating on the two ends of the rocker beam, one by the linkage from the control arm and the other by the linkage from the pressure sensitive diaphragm.

It is also apparent that the beam is the meeting point for the two counteracting forces, i.e., forces from the control arm 28 and yfrom the pressure sensitive diaphragm. The operation ofthe beam acts upon the pressure plate 121 as does the diaphragm. The pressure plate in turn actuates the switches which are supported above the pressure plate. These switches can be supported in `any convenient manner the main desideratum being that their positions may be independently adjusted in relation to the plate so that upon movement of the plate they operate in the desired sequence.

It has been found expedient to use a minature type of switch well known in the industry as a micro-switch.

As best shown in FIG. 7, the legs 132 of the bracket 132-133 have a support rod 170 secured thereon. From the support rod two pairs of arms 171 extend forwardly over the pressure plate 121 and each pair carries between them a micro-switch, such as S1 and S2. The arms `of each pair are separated from the other pair by a sleeve 17d. Each of the outer of the arms 171 is provided with a laterally extending lug 172, FIGS. 4 and 5. Each of the lugs has a screw 173 extending loosely therethrough and screw threaded into the base 50. A helical spring between the lug and base around the screw holds the arm against the head of the screw. Thus each of the switches may be independenly adjusted as to its height above the pressure plate 121. The operating pins on the switches are disposed opposite to the plate 121 so that movement of the plate may actuate the pins which in turn cause the internal switch mechanism to operate in a conventional manner.

The unit is adapted to operate on alternating current of 24, 115 or 230 volts. In FlG. 11, the power lines 110 volts being connected to the terminals 1 and 2. Terminal 2 is connected directly to the mid-terminal of the motor 25. As stated, the motor 25 is a reversible motor the direction of rotation being `controlled by the application of current to one or the other of the outside terminals.

When the pressure differential being sensed increases as it would be at the start of a period when the air is increased and it is desired to supply fuel in amount proper for amount of air supplied, the diaphragm is moved downward. This causes the motor to be energized and the control arm to move outward. Energization is effected by switch S2 which is moved to its closed contact position wherein current is supplied from terminal 1 to the switch blade and from the closed contact to the S2 terminal, from there by the jumper to No. 4 terminal and from there through the closed `outer limit switch 200 back to the motor. The motor is then energized and the control arm is moved outward.

As shown in FlG. 2, there are two limit switches 200 and 201 having control arms 200 and 201 disposed to be engaged by lugs 202 and 202 carried on the nut 27 on the control arm. The switches are disposed in the circuit so as to open the circuit upon extreme movement of the control arm as a mechanical safety factor.

When the control arm 28 moves outward, its connection by the link 29 to the fuel valve causes that valve to open and admit fuel to the burner. At the same time the cam plate 30 causes the operation of the arm 62 which swings the cam 81. The cam 81 transmits movement from the cam plate 84 to the bell-crank lever 106 which presses down on lthe beam 92, raising the right hand end, FIG. 2, and in turn raising the arm 143, which pressure is transmitted through the arm 1142 to the diaphragm rod, this pressure being in opposition to the pressure on the diaphragm.

It will be appreciated that the above action is not necessarily a sudden action as a result of a sudden large differential but is usually a gradual action caused by a slight drop in steam pressure. The amount of drop in steam pressure would vary with the demand upon the boiler.

In any event when a demand is present the above action takes place and after the control arm has been moved to a predetermined position and the fuel supplied in the proper ratio to the air being supplied, `the upward pressure by the beam on the diaphragm offsets the pressure by the diaphragm and the pressure plate is raised to cause the opening of the switch S2. The ratio of fuel to air is controlled by the position of the beam 92 which is adjusted by the screw 166.

Upon the predetermined amount of upward movement of the diaphragm the movable arm or switch S2 moves upward and makes contact with the normally open contact supplying current to the switch S1 through the Contact arm which is still at the normally open position. The two switches are adjusted so that the movement of S2 moves the contact arm ahead of switch S1.

The motor being deenergized, the control arm no longer moves and a neutral position is achieved until such a time as the steam pressure builds up. When the steam pressure rises above the desired value, the master control is operated to decrease the air supply. The present unit immediately senses this decrease in air supply and the diaphragm moves up moving the contact arm of switch S1 to the upper contact. Since current is already supplied to the contact arm through switch S2 it passes through the Cil switch S1 out the `upper control'to terminal S1 and from there `to terminal 3, through the inner limi-t switch 201 which is normally closed, back down the line to the third terminal on the motor. operate in the reverse direction to move the control arm inward and reduce the fuel supply.

Since the movement of the control arm 2S is now in*- ward, the cam 31 is rocked in the opposite direction and the pressure on the beam 92 is released, and the upward pressure on the pressure plate 121 is released so that the plate which had moved upward in response to a decrease in pressure difference on the diaphragm now moves downward. This causes switch S1 to lopen the motor circuit and the control arm stops. This can be termed a neutral position and the circuits are now all open, switch S1 being in the down position and switch S2 in the up position.

Should the demands on the boiler become less and the pressure again rise, the air supply would be still further decreased and the control arm would move in still further and the cycle repeat itself.

In practice the contour of the cam plate 84 is adjusted so that the control arm 28 moves out to the proper position to provide the desired amount of fuel for the air being admitted to the burner. This is determined by CO2 measurements in the stack, the air being controlled manually from minimum to maximum and the cam contour screws adjusted so that the proper amount of fuel is supplied for each setting of the air supply. lt will `be apparent that yby adjusting the contour cam the movement of the control arm can be adjusted and that the position of the control arm is determined by the amount of fuel being admitted through the valve 21. Thus the valve 21 ceases to be 1a cri-tical factor from the standpoint of its construction and much cheaper and rugged valves can be used than Iwas heretofore possible.

The ratio of fuel to air required may vary with different types of fuel, that is one fuel may require a different ratio to another. This ratio can be quickly and accurately controlled by the sliding of the beam 92 by the convenient knob '.101 on the front panel.

Certain other characteristics of the system may also be controlled to provide for more efficient operation.

These include a range adjustment by the screw 166 which controls the effective length of the spring 155. As the effective length is decreased the spring is stiffened decreasing the range and if the spring is effectively lengthened, the range is increased.

This is useful because the pressure differential may vary with different installations. One installation may have a pressure range of from 0 to 3 lbs., and another from `0 to 5 lbs. or even less than 3 lbs. rIhus the tension of the spring 15S may be adjusted for the particular range with which the device is used.

The sensitivity of the device may also be adjusted by the screws 173 which raise or lower the switches S1 and S2 and determine their respective positions with respect to the pressure plate 121. This is desirable especially in systems having a low capacity and a high demand where a quicker response to demand is required, or in cases where it is desired to keep the steam pressure Within closer limits of a desired pressure and the time lag should be reduced to a minimum.

The screw 148l which adjusts the position of the roller 147 with respect to the beam 92 is a zero adjustment which enables a balance to be obtained between the pressure due to the control arm operated bell-crank lever and the pressure exerted by the diaphragm 19. This might also be termed a neutral adjustment because it enables the pressure applied to the beam 92 to be balanced so that the switches S1 and S2 can attain a neutral control position, assuring the stopping of the motor 25.

The spring 150 which loads the arm 143` is ordinarily adjusted at the factory to maintain proper pressure on the This causes the motor to' arms 142-143 and to eiect a balance between those arms and the diaphragm.

llt will thus be seen that I have provided a control unit which may be used to control valves of ordinary, cheap and rugged construction and wherein the opening of the valve may be quickly and accurately controlled according to the demand for fuel. It is also apparent that the device is useful in a large and wide variety of diierent installations since it can be adjusted for the particular installation easily and quickly. Furthermore, it provides i a means of quickly adjusting the same to provide the desired fuel air ratio for the particular fuel being used.

lt will also be noted that although only one unit is used for metering the fuel, that the device would be useful where two units could be used, one for controlling fuel and ythe other air, to provide full metering for the system. In this case the master regulator would be replaced by another unit, such as described, which would be connected -to the air controlling member 14.

Having thus described my invention in an embodiment thereof, I am aware that numerousl and extensive departures may be made therefrom without departing from the spirit of the invention as defined in the appended claims.

I claim:

l. An apparatus for the control of the admission of a combustion component into a steam boiler combustion chamber wherein air land fuel Vcombustion components are `admitted through a burner `and wherein the flow of one of said components is controlled by the steam pressure in the boiler, comprising a frame, a pressure sensitive member movable -responsive to the flow of one of said components disposed below the frame, a switch operating plate hingedly supported at one end to said frame and means connecting said pressure sensitive member to the switch operating plate through the free end of the plate, a pair of arms hingedly supported at one end of the frame above the switch operating plate, said pressure sensitive member being connected to lone of said arms for transmitting movement thereto and the point of connection including a leaf spring carried by one of the arms and clamp means slidable along the arm and spring and arranged to clamp the spring to the arm at diierent positions longitudinally of the arm and spring to vary the effective length of the spring, a support slidably disposed on the frame opposite one of said arms and a tlever carried by the support and having ends extending in opposite directions from the support, said support comprising a fulcrum for the levers, means Ito move the support along the frame including a nut member on the support disposed below the frame and a screw supported below the frame and engaged in the nut member and means carried by the frame and connected to Ithe screw for rotating the screw and moving said support, one of said arms having a roller carried thereby, said roller resting on said lever to one side of the fulcrum and means to adjust the position of the roller relative to the arm, and spring means connected between said arm and the frame for moving the arm with the roller into engagement with the lever, means for controlling the iiow of the other component including a reversible motor and a control arm connected there-to and movable longitudinally in response to energization of the motor by a motor circuit, a second lever connected to said control arm, a cam connected to and actuated by said second lever, a lever having a cam engaging portion in engagement with the cam and a first lever engaging portion for pressure engagement with the other end of the first lever, a motor circuit and switch means for controlling the motor circuit, means for adjustably supporting said switch means in operative connection with said switch operating plate.

2. A device as described in claim 1, wherein said switch means comprises a pair of discrete switch means each connected into the motor circuit and each adjustable independently of the other with relation to the switch operating plate.

3. An apparatus for the control of the admission of a combustion component into a steam boiler combustion chamber wherein air and fuel combustion components are admitted through a burner and wherein the flow of one of said components is controlled by the steam pressure in the boiler, comprising a frame, a pressure sensitive member ymovable responsive to the flow of one of said components disposed below the frame, a switch operating plate hingedly supported at one end to said frame and means connecting said pressure sensi-tive member to the switch operating plate, a pair of arms hingedly supported alt one end of the frame above the switch operating plate, said pressure sensitive member being connected to one of said arms for transmitting movement thereto and the point of connection including a leaf spring carried by one of the arms and clamp means slidable along the arm and spring and arranged to clamp the spring to the arm at different positions longitudinally of the arm and spring to vary the effective length of the spring, a support slidably disposed on the frame opposite one of said arms and a lever carried by the support and having ends extending in opposite directions from the support, said support comprising a fulcmm for the lever, means to move the support along the frame including a nut on the support disposed below the frame and a screw supported below the frame and engaged in the nut and means carried by the frame and connected to the screw for rotating the screw and moving said support, one of said arms having a roller carried thereby, said roller resting on said lever to one side of the fulcrum and means ito adjust the position ofthe roller relative to the arm, and spring means connected between said arm and the frame for moving the arm with the roller into engagement with the lever, means for controlling the flow of the other component including a reversible motor and a control arm connected thereto and movable longitudinally in response to energization of the motor by a motor circuit, a second lever connected to said control arm and a cam body connected to and actuated by said second lever, said cam comprising a semi-circular body and having a llexible cam plate on one side of the body, cam plate adjusting screws extending through said body and engaging said cam plate for adjusting the contour of the cam plate, a bell-crank lever having a cam engaging portion in engagement with the cam and a iirst lever engaging portion for pressure engagement with the other end of the first lever, a motor circuit and switch means for controlling the motor circuit, means for adjustably supporting said switch means in operative connection with said switch operating plate.

4. An apparatus for the control of the admission of a combustion component into a steam boiler combustion chamber wherein air and fuel combustion components are admitted through a burner and wherein the flow of one of said components is controlled by the steam pressure in the boiler, comprising a frame, a pressure sensitive member movable responsive to the iiow of one of said components disposed below the frame, a switch operating plate hingedly supported at one end to said frame and means connecting said pressure sensitive member t-o the switch operating plate, a pair of arms hingedly supported at one end of the `frame above the switch operating plate, said pressure sensitive member being connected to one of said arms for transmitting movement thereto and the point of `connection including a leaf spring carried by `one of the arms and clamp means slidable along the arm and spring and arranged to clamp the spring to the arm at diierent positions longitudinally of the arm and spring to vary the effective length of the spring, a support slidably disposed on the frame opposite one of said arms and a lever carried by the support and having ends extending in opposite directions from the support, said support comprising a fulcrum for the levers, means to move the support along the frame including a nut on the support disposed below the frame and a screw acct-5,020

lll

supported below the frame and engaged in the nut and means carried lby the frame and connected `to the screw for rotating the screw and moving said support, one of said arms having a roller carried thereby, said roller resting on said lever to one side of the fulcrum and means to adjust the position of the roller relative tothe arm, and spring means connected between said arm and the frame for moving the arm with the roller into engagement with the lever, means for controlling the flow of the other component including a reversible motor and a control arm connected thereto and movable longitudinally in response to energization of the motor by a motor circuit, a second lever connected to said control arm, a cam connected to and actuated by sai-d second lever, a lever having a cam engaging portion in engagement with the cam and a rst lever engaging portion for pressure engagement with the other end of the first lever, a motor Circuit and switch means for controlling the motor circuit, means for adjustably supporting said switch means in operative connection with said switch operating plate.

5. An apparatus for the control of the admission of a combustion component into a steam boiler combustion chamber wherein air and fuel combustion components are admitted through a burner and wherein the flow of one of said `components is controlled by the steam pressure in the boiler, comprising a support, a pressure sensitive member movable responsive to the 110W of one of said components carried by the support, a switch operating member carried by said support and means connecting said pressure sensitive mem-ber to the switch operating member, lever means supported at one end of the frame opposite the switch operating member and said pressure sensitive member being connected to said lever means for transmitting movement thereto, a fulcrum disposed on the support opposite said lever means and a second lever carried by the fulcrum and having ends extending in opposite directions therefrom, means carried by said first lever and contacting said second lever to one side of .the fulcrum and means to adjust the contact position of the rst lever with the second lever, land means connected between said first lever and the `frame for moving the lever into engagement with the second lever, means for controlling the iiow of the other component including a reversible motor and a control arm connected thereto and movable in response to energization of the motor by a motor circuit, a third lever connected to said control arm, a cam connected to and actuated by said third lever, a fourth lever having a cam engaging portion in engagement with the cam and a portion for pressure engagement with the other end of the second lever, a motor circuit and switch means for controlling the motor circuit, means for adjustably supporting said switch means in operative connection with said switch operating member.

6. An apparatus as described in claim 5, wherein said fulcrum is movable on the support to vary the ratio of the second lever arms.

References Cited in the le of this patent UNITED STATES PATENTS 1,167,343 Gibson Jan. 4, 1916 2,052,375 Wunsch et al Aug. 25, 1936 2,053,885 Weeks Sept. 8, 1936 2,125,949 OConner Aug. 9, 11938 2,145,305 Hull lan. 31, 1939 2,166,077 Spitzglass July 11, 1939 2,197,171 Annin Apr. 16, 1940 2,412,739 McCracken Dec. 17, 1946 2,437,551 Penn Mar. 9, 1948 2,546,657 Smoot Mar. 27, 1951 2,624,868 Runnnger Jan. 6, 1953 2,748,613 Guay .Tune 5, 1956 2,875,622 Nichols Mar. 3, 1959 

1. AN APPARATUS FOR THE CONTROL OF THE ADMISSION OF A COMBUSTION COMPONENT INTO A STEM BOILER COMBUSTION CHAMBER WHEREIN AIR AND FUEL COMBUSTION COMPONENTS ARE ADMITTED THROUGH A BURNER AND WHEREIN THE FLOW OF ONE OF SAID COMPONENTS IS CONTROLLED BY THE STREAM PRESSURE IN THE BOILER, COMPRISING A FRAME, A PRESSURE SENSITIVE MEMBER MOVABLE RESPONSIVE TO THE FLOW OF ONE OF SAID COMPONENTS DISPOSED BELOW THE FRAME, A SWITCH OPERATING PLATE HINGEDLY SUPPORTED AT ONE END TO SAID FRAME AND MEANS CONNECTING SAID PRESSURE SENSITIVE MEMBER TO THE SWITCH OPERATING PLATE THROUGH THE FREE END OF THE PLATE, A PAIR OF ARMS HINGEDLY SUPPORTED AT ONE END OF THE FRAME ABOVE THE SWITCH OPERATING PLATE, SAID PRESSURE SENSITIVE MEMBER BEING CONNECTED TO ONE OF SAID ARMS FOR TRANSMITTING MOVEMENT THERETO AND THE POINT OF CONNECTION INCLUDING A LEAF SPRING CARRIED BY ONE OF THE ARMS AND CLAMP MEANS SLIDABLE ALONG THE ARM ND SPRING AND ARRANGED TO CLAMP THE SPRING TO THE ARM AT DIFFERENT POSITIONS LONGITUDINALLY OF THE ARM AND SPRING TO VARY THE EFFECTIVE LENGTH OF THE SPRING, A SUPPORT SLIDABLY DISPOSED ON THE FRAME OPPOSITE ONE OF SAID ARMS AND A LEVER CARRIED BY THE SUPPORT AND HAVING ENDS EXTENDING IN OPPOSITE DIRECTIONS FROM THE SUPPORT, SAID SUPPORT COMPRISING A FULCRUM FOR THE LEVERS, MEANS TO MOVE THE SUPPORT ALONG THE FRAME INCLUDING A NUT MEMBER ON THE SUPPORT DISPOSED BELOW THE FRAME AND A SCREW SUPPORTED BELOW THE FRAME AND ENGAGED IN THE NUT MEMBER AND MEANS CARRIED BY THE FRAME AND CONNECTED TO THE SCREW FOR ROTATING THE SCREW AND MOVING SAID SUPPORT, ONE OF SAID ARMS HAVING A ROLLER CARRIED THEREBY, SAID ROLLER RESTING ON SAID LEVER TO ONE SIDE OF THE FULCRUM AND MEANS TO ADJUST THE POSITION OF THE ROLLER RELATIVE TO THE ARM, AND SPRING MEANS CONNECTED BETWEEN SAID ARM ND THE FRAME FOR MOVING THE ARM WITH THE ROLLER INTO ENGAGEMENT WITH THE LEVER, MEANS FOR CONTROLLING THE FLOW OF THE OTHER COMPONENT INCLUDING A REVERSIBLE MOTOR AND A CONTROL ARM CONNECTED THERETO AND MOVABLE LONGITUDINALLY IN RESPONSE TO ENERGIZATION OF THE MOTOR BY A MOTOR CIRCUIT, A SECOND LEVER CONNECTED TO SAID CONTROL ARM, A CAM CONNECTED TO AND ACTUATED BY SAID SECOND LEVER, A LEVER HAVING A CAM ENGAGING PORTION IN ENGAGEMENT WITH THE CAM AND A FIRST LEVER ENGAGING PORTIN FOR PRESSURE ENGAGEMENT WITH THE OTHER END OF THE FIRST LEVER, A MOTOR CIRCUIT AND SWITCH MEANS FOR CONTROLLING THE MOTOR CIRCUIT, MEANS FOR ADADJUSTABLY SUPPORTING SAID SWITCH MEANS IN OPERATIVE CONNECTION WITH SAID SWITCH OPERATING PLTE. 